/SamXIAO
#include <bits/stdc++.h>
using namespace std;
#define PI 3.1415926
#define   SQUARE(x) ((x)*(x))
//double SQUARE(double x) { return x*x;}
#define N_MAX 987654321
#define N_MIN -N_MAX
int f[286];
char s1[1086];
char s2[2020];
void w1()
{
	int cnt = 0, ans = 0, n;
	scanf("%s", s1);
	bool isOk = true;
	for(int i=0; i<strlen(s1); i++) {
		char ch = s1[i];
		if(  ('0' <= ch && ch <= '9')
			|| ('a' <= ch && ch <= 'z')
			|| ('A' <= ch && ch <= 'Z')
			|| '_' == ch){
			if(('0' <= ch && ch <= '9') && 0 == i) isOk = false;
		}
		else{
			isOk = false;
		}
	}
	printf("%s", isOk ? "yes" : "no");
}

int main()
{
	w1();
  return 0;
}
